A mastery of water-use techniques by civilization has been evidenced for thousands of years, one high point being reached with the development by the Romans of long-distance water transportation. Within the current century, the introduction of practical turbine pumps, large scale water storage and practical water transmission networks has greatly expanded public water supply systems. See in this regard:
I. "Technology in American Water Development" by Ackerman and Lof, the Johns Hopkins Press, Baltimore, Md. PA0 II. "Pipeline Design for Water Engineers" by Stephenson, Elsevier Scientific Publishing Company, New York, 1981.
Concomitant with the expansion of water transmission networks has been the development of improved piping techniques. For example, the DeLavaud process permitted a practical and improved centrifugal casting of pipe used in water supply networks, while in about 1948 further improvements in pipe construction were evidenced by the development of ductile iron pipe having important strength and corrosion resistance properties. To provide for practical assembly of pipeline matrix components, a variety of joining devices and techniques have been developed. The more popular of these approaches to joining pipe is referred to as a "bell-and-spigot" joint or push joint which is made by slipping a male or spigot end of one pipe section into the bell end of an adjacent pipe essentially until contact is made at the base of the bell. A flexible gasket positioned within the joint assures its water-tight integrity. As may be apparent, this construction is popular both due to the lowering of labor requirements for assembly and due to the simplicity and lower cost of pipes intended for such joining provisions.
A related joining approach utilized principally in the assembly of tees, elbows and plugs provides a mechanical joint wherein a flange is fabricated on one end of such a component or pipe length and a ring-shaped gland is positioned over the adjacent pipe end. By bolting the flange and gland together such that a flexible seal at the joint is compressed, a water-tight union is achieved. The pull-apart resistance or strength of such joint has been enhanced through the use of set screws in conjunction with the bolted gland, however, resort to such a joining technique in typically encountered lengthy runs of piping is both impractical and unduly expensive.
The design of a municipal piping matrix necessarily involves very long pipelines evidencing numerous directional changes and the resultant use of elbows and attendant joints, tee components leading to fire hydrants or user entities, as well as caps terminating a given matrix branch. Piping also may be joined, as well as repaired by sleeve type coupling devices. Such steel couplings are particularly useful where transitions are called for between pipes of different classes or sizes. Not only are bursting pressure stresses, pipe weight considerations, superimposed loads as are associated with backfill, water hammer stresses and the like contemplated by the designer, but also the longitudinal forces which become active whenever there is any change in the horizontal or vertical alignment of a length of pipeline must be accommodated for. In this regard, see the following publication:
Without an appropriate accommodation, these longitudinal forces will cause pipe joints to separate. Accordingly, early pipeline design approaches resorted to the use of concrete thrust blocks at each pipeline bend which were structured to counteract: (a) the dynamic thrust due to change in direction of water flow, and (b) the thrust in the direction of each leg of a bend due to water pressure in the pipe.
One successful approach to assuring joint integrity against the above-described thrust forces has been through resort to tying techniques wherein spaced but adjacent flanged joint components are tied together by elongate thrust rods. To simplify the tying procedure, such innovations as "Tiebolts" have evolved to simplify thrust rod placement. See in this regard U.S. Pat. No. 3,144,261. A condition often occurs wherein the thrust rods used in tying a direction changing joint to an elongate run of pipe presents a condition wherein an anchoring flange is not available to provide a rearwardly disposed thrust rod connection. Under these conditions, a retainer clamp has been affixed to a length of such rearwardly disposed bell-and-spigot jointed pipe. Generally, the clamps have been of purely conventional design, two clamp components being bolted over the outer circumference of the pipe and retained in place on the pipe by clamping pressure. Thrust rods then were attached to the clamp outwardly of the bolts holding the clamp to the pipe and extended along and parallel to the pipe for attachment to the flanged component. In order to obtain adequate anchorage, the assembly team must position the retainer clamp a sufficient distance rearwardly along the length of pipe to provide for the resistances achieved by the mass of pipe itself, friction with the trench, associated back fill and the like. As a consequence, thrust rods of lengths approaching 200 feet have not been an unusual encounter.
Tests of the traditional retainer clamps have revealed that they are prone to excessive slippage under the thrust rod loads now evidenced in conventional piping systems. As is apparent, the amount of this thrust will vary in correspondence with the size of pipe utilized. One approach taken to improve anchoring capabilities for thrust rods is described in a copending application for U.S. Ser. No. 374,000 by the inventor hereof filed May 3, 1982, and entitled "Thrust Rod Anchor for Pipe Joint Restraint Systems" and now U.S. Pat. No. 4,492,391. While achieving significantly improved anchoring performance, the anchor described in the application is designed such that the thrust rods are incorporated in close proximity to the outer surface of the pipe itself when installed. As a consequence, the device cannot be used where the thrust rods must pass over intermediately disposed sleeves or couplings and the like. It has been determined that a considerable number of applications require a feature wherein the thrust rods are outwardly disposed from the pipe to permit passage over intermediately disposed connecting components. Additionally, it is important that the tie rods be installed such that there is no contact between the tie rods themselves and the surface of the pipe. A further difficulty resides in the use of set screws which are conventionally incorporated in the anchor to enhance the anchoring capabilities thereof. Typical set screws are configured having knurled tips which tend to extend excessively into the surface of the pipe on which the anchor is to be installed. Anchoring structures have been observed to warp or stretch in the course of their installation. As a consequence, installing personnel have caused the set screws to be rotated an excessive amount to achieve desirable torque. For example, preferred set screws are configured having a break-off portion to which the installer applies a wrench and rotates the set screw until such time as about 80 foot pounds torque is achieved whereupon the portion engaged by the wrench is sheared off. Where excessive rotation occurs due to clamp warpage or the like, this additional rotation required of the set screws causes them to "drill" into the pipe surface an excessive amount. In some instances this drilling effect will extend completely through a pipe wall. Where softer iron pipe is encountered, it is desirable that lower torques be employed in tightening set screws to avoid excessive drilling.
Another aspect involved in the utilization of tie rod anchor structures resides in the installation of the anchors and tie rods within the trenches or similar environment of their use. For example, many prior anchor structures involve an installation procedure wherein set screws or bolts must be tightened while they are positioned on the underside of the pipe upon which the anchor is being installed. The difficulties of such installation are apparent. It is desirable that the tie rods and all bolts or the like which must be tightened during installation be readily accessible to the installer from the top or side of the pipe.